Hello,
This error is usually caused by a bad connection, either a lack of internet connection or the game server being down. What server are you attempting to connect to? I can't quite make it out on your screenshot.
Thanks!

I don't seem to have access to this server. Are you sure that's the correct server number?

OK, Sorry that took so long, we finally managed to track your server down. You are S1353:Double-Oboro Clone | HK. The discrepancy in number and spelling made it harder to find, sorry about that.

I was able to log into your server without any difficulties, so the server is online and working. If you are still experiencing this error, it means that you are suffering from a lack of connection. usually this error means a total lack of connection, period. Usually we also see this error if you cannot connect to the login server, but since I was able to login, that is not the case. Is your connection to other sites OK, or are you making this post from another device?